Take the PSAT in October. The scores will not count for National Merit Scholar consideration in your sophomore year, but it is valuable practice for when you take the PSAT again in your junior year (when the scores will count), as well as for the SAT I exam which you should also be taking in your junior year. You will receive your PSAT results in December. Don't forget to start preparing for the SAT.

Register, in April, for the SAT II for any subjects you will be completing before June.